Electrical control for centrifugal separating machines



3 Sheets-Sheet 1 J. s. PECKER Filed Dec. 26, 1954 May 18 1937.

ELECTRICAL CONTROL FOR CENTRIFUGAL SEPARATING MACHINES [NV NTOR ATTORN EY May 18, 1937. 5, PECKER 2,080,874

ELECTRICAL CONTROL FOR GENTRIFUGAL SEPARATING MACHINES Filed Dec. 26, 1934 s Sheets-Sheet 2 May 18, 1937. J 5. PECKER 2,080,874

ELECTRICAL CONTROL FOR CENTRIFUGAL' SEPARATING MACHINES Filed Dec. 26, 1954 5 Sheets-Sheet 3 INVE TCI R ATTORNEY Patented May 18, 1937 ELECTRICAL CONTROL FOR CENTRIFUGAL SEPARATING MACHINES Joseph S. Pecker, Philadelphia, Pa., assignor to American Centrifugal Corporation, New York, N. Y., a corporation of Delaware Application December 26, 1934, Serial No. 759,302

36 Claims.

This invention relates to the control of electrically driven centrifugal machines and is particularly concerned with the control and cyclic operation of such machines used to extract-the solid matter from sewage and other sludge.

The invention relates to means for slowly starting a centrifugal basket and setting into operation means for cleaning the basket, increasing the speed for normal operation, admitting sewage sludge and operating for a definite time cutting off supply of sewage sludge, slowing down the basket, and again cleaning. This cycle of operations is continued indefinitely, and automatically operating means is provided for that purpose.

An object of the invention is to provide a slow speed motor for starting and low speed operation, and a high speed motor for normal operation of the centrifugal machine, and to electrically interlock the circuits of these machines so as to bring about the desired sequence of operation of the motors.

A further object is to provide one or a plurality of cleaning blades in the basket for scraping the deposited material from the inner wall and moving it toward the center of the bottom of the basket where it passes out, these blades being intermittently operated in their movement from and toward the wall of the basket. A further object of the invention is to provide an electrical control adapted not only to provide a means for intermittently or periodically operating the scrapers or cleaning blades but which will also permit a continuous movement outwardly and inwardly of the cutters or scrapers. Another object is to interlock the circuits of the slow speed driving motor with the cleaner operating motor so as to bring about proper cooperation of these devices in cleaning the basket.

It is also an object to interlock the circuits of the inlet valve motor with those of the high speed motor and to provide time controlled means for controlling the operation of these motors. Other objects will be apparent from the detailed description of the apparatus.

Referring to the drawings, which are made a part of this application and in which similar reference characters indicate similar parts:

Fig. l is a side elevation of a centrifugal ma-' Fig. 4 is a diagram of the control and operating circuits of the machine.

Referring to Figure 1, the centrifugal machine is indicated generally at I, the low speed driving motor at 2, the high speed motor at 3, the cleaner driving motor at 4, the inlet valve at 5 and the valve operating motor at 6. While the inlet valve 5 and the valve operating motor are shown in the accompanying drawings located at the top of the centrifugal separating machine, it will be readily understood that they may be located at any other desiredpoint but controlled, nevertheless, from the control panel. The basket of the machine is located above and is driven through gearing located in the gear casing l. The slow 5 speed motor 2 is connected to the driving gears in casing through a free wheeling or overrunning clutch 8 so that the slow speed motor will not be driven while the high speed motor is in operation, but will drive through the clutch 8 when the speed of the extractor has dropped to such an extent that the clutch can operate. While the motors 2 and 3 are referred to as low and high speed motors it will be appreciated that the speeds of these motors may so vary as to more nearly approach the same speed, particularly when changing over from cleaning to purging operation. The cleaning mechanism within the basket of the machineis operated by the screw 9 which is reciprocated by the reversible cleaner motor 4 through the bevel gears l0 and II. This motor 4 is controlled by reversing and limit switches shown in Figure 3 in interlocking relation with the other circuits of the system of control. A centrifugal governor I2 is driven by the high' speed motor and controls the interlocked switches in the operating circuits of the high, and low speed motors. While a centrifugal ball type governor has been shown as a speed responsive means 40 for controlling the motors it will be understood that type of device is illustrative and that other speed responsive means, known in the art, electric or fluid operated, for instance may be employed to perform this function.

In Figure 2 is shown in plan and in enlarged scale the construction below the section on line l-l of Figure 1. In this figure the plate l3 has mounted thereon the screw Q for operating the cleaning blades or scrapers i4, l5 which are 10- cated in the basket, shown in section at It, and below the plane of plate l3. These cleaning blades i and I5 are oscillated by means of rods H and I8 which are mounted in plate l3 and are themselves oscillated by arms 20 which have projections 2i and 22 extending into openings in an extension 23 of the screw 9. This extension member 23 has a sliding bearing at 24 mounted on plate 13. It will be apparent that upon rotation of gear H in reverse directions the member 23 will be reciprocated and due to the connection between the arms 20 and member 23, the rods I! and I8, and the blades H3 and [5 will be oscillated. These blades have cutting edges 24 and 25 which on outward movement of the blades engage and slice the material deposited on the inner wall of the basket as indicated at 25. When substantially all of such material has been detached from the basket wall the finger '21, integral with one of the arms 20, engages and closes limit switch 23 which reverses the cleaner driving motor 5 which moves the blades in a step-by-step manner towards the center of the basket. In this movement the blades scrape the dried solids of the sludge on the bottom of the basket towards the center and such material drops through openings in the bottom and is carried away. The blades continue towards the center of the basket until finger 27 engages limit switch 29 which reverses the motor 4 again and this cycle is repeated subject to other controls which will be explained.

Figure 4 is a general wiring diagram of the control and operating circuits of the motors and should be considered in connection with Figure 3 which shows additional connections in detail for control of the cleaning motor by limit switches operated thereby. In Figure 4 the line L1, L2 supplies current to all of the motors and other auxiliary apparatus, or certain of the auxiliary devices such as the timing clocks or telecrons may be supplied from separate sources.

The main line switch 39 may be manually or electromagnetically operated and an additional line switch may be employed to be controlled by a push-button or push-buttons located in convenient position at the machine.

The circuit of the low speed motor 2 may be traced '(Figure 4) from L1, switch 30, line 3|, switch 3, connection 32, 32', motor 2, 32", connection 33 to line 34, through switch 30 to L2. The operating circuit of the cleaner motor 6, is from connection 32, on the motor side of switch I 3, through 35, reversing switch 36, jogging switch 31, motor 4, lead 38, reversing switch 37 and leads 39 and 33 to L2. It will be apparent that when switch I3 is closed motor 2 will be energized and motor 4 will also be energized subject to the intermittent control by the jogging switch 31 the operation of which will be explained later.

The operation of the high speed motor 3 is from \lead 3!, reversing or plugging switch 42, lead 93, motor 3, lead M, switch 45, lead 46, switch 62 to lead 3 3 to line L2.

The valve operating motor 3 is connected in parallel with motor 3 on the motor side of its controlling switch so that it can be operated only during the operation of the high speed motor. The operating circuit of motor 6 is from lead 53, lead 91, motor 5, lead 48, switch 49, lead 59 to lead 59. Motor 6 is also provided with a reversing circuit since it must reverse in order to open and close the inlet valve to the machine. The reverse circuit for motor 5 is from il, motor 5, lead 5!, switch 52, lead 53, lead 50 to lead i l. Switches 59 and 52 are interlocked so that both cannot be closed at the same time. This interlock is indicated at 59. Switch 59 is electromagnetically operated by a coil 55 which is controlled by a timing device 56 which may be an electric clock or telecron. Switch 52 is electromagnetically operated by a coil 5! controlled by a timing device 58 similar to 56. The timer 58 can be regulated to open the valve at a predetermined time and while the high speed motor is going up to maximum speed. The timer 58 is arranged to predetermine the length of time that the valve is open which predetermines the quantity of material allowed to flow into the basket. The closing of the valve at the time set by the timer 58 will not affect the operation of the high speed motor. This motor 3 is controlled through the reversing or plugging switch 42 by another timer 59 controlling coil 60.

Coil 15 controls switches l3 and 45 and is itself controlled by the governor l2 driven by the high speed motor. When this motor is'not running or is slowed down to a predetermined low speed the contacts controlled by governor l2 are closed, and if the line circuit is closed coil 15 will be energized to close switch l3 and open switch 45. If the machine is not running, and the line circuit is closed coil 75 will be energized to open switch 45 and close switch I3. Switch [3 will then be held in closed position by holding coil 9 which is controlled by limit switch 29 (Figure 3).

Referring to Figure 3, the operating circuit for the cleaner motor 4 is the same as that described in Figure 4. The reversing switch 36 of this motor is controlled by two coils BI and 62 which are controlled by the limit switches 28 and 29 which are operated by the finger '21 operated by the arm 29 which is in turn driven by the motor l, through II], II, 9 and 23. Coil BI is energized through the following circuit from connection 33, leads 63, 6t, coil 6|, lead 65, limit switch 29, leads 66, 61 to connection 3| The cir cuit for coil 62 is from connection 33, lead 63, coil 62, lead 68, limit switch 29, lead 69, lead 6! to connection 3!. It will be noted that limit switch 29 has two operative positions. When switch 29 is in the position shown the circuit of coil 62 is closed. When in the other operative position the holding coil 9 of switch 13 is energized. The circuit for coil 9 is from connection 33, lead 10, coil 9, lead H, left-hand contact of switch 29, lead 69, lead 6'! to connection 3|. Switch 29 is biased to its left-hand closed position normally.

The jogging switch 31 is operated by the jogging timer cam [9 which is driven by the jogging motor 12. This motor 12 is connected in parallel with the low speed motor 2 through the following circuit. from connection 33, lead 13, motor 12, lead 14 to connection 32. It will be apparent therefore that motor 12 will be energized whenever motor 2 is energized.

The circuits of coils 55, 51, 60, and 15 are not shown completed to avoid confusing the drawings with too many lines. It will be understood that these coils are connected to the line L1, L2 on the machine side of the main switch. Likewise the usual protective devices for the motors, such as accelerating devices, overload circuit breakers, under voltage controls, and automatic setting of the timing devices, mechanical interlocks and details of adjustment are omitted for the sake of clearness.

In Figure 4 the reversing or plugging switch I 42 is set normally for forward running of the high speed motor. This switch is moved to its reverse position by coil 69 for the purpose of plugging or decelerating by reversing its current supply. The time for energizing coil BI] and the duration of its energization is controlled by the automatic timer 59. In like manner timer 56 fixes the time of energization of coil 55 to start valve motor 8 in operation which may be at the time the high speed motor attains normal speed or shortly thereafter. The timer 58 determines how long the valve shall remain open and so determines the quantity of sludge to be supplied to the basket for one cycle of operation. The inlet valve 5 may be manually closed by means of hand wheel I6 in case of failure of theline current during operation of the machine.

The operation of the machine is as follows: The line switch 30 is closed manually or by pushbutton control on the machine, at this time the contacts controlled by governor I2 are closed so that coil 15 is energized and closed switch I3, opening switch 45, and slow speed motor 2 is set into operation. Limit switch 29 is in the position shown in Figure 3. The jogging motor 12 in parallel with motor 2 will be energized and begin rotating cam I9. If switch 31 is in closed position cleaner motor 4 will begin to rotate to move the cleaner blades I4 and I5 outwardly towards the wall of the basket. If switch 31 is not in closed position motor 12 will close it shortly after this motor becomes energized and will continue to open and close it so long as the low speed motor is energized. The cleaner blades will be given a step-by-step movement in their .outward and inward travel. This is for the purpose of cutting ofi the accumulated material on the inner wall in layers and giving it time to pass out through openings in the bottom of the basket as the blades scrape it towards the center as they return towards that position. As soon as blade I5 moves outwardly the finger 2I releases limit switch 29 (Figure 3) and it closes the circuit of holding coil 9 of switch I3. When the cleaner blades reach their maximum outer position the finger 2! closes limit switch 28 which energizes coil 6| of reversing switch 35 which reverses motor 4 and the blades are returned to their inner or central position by a step-by-step movement scraping whatever material is in the basket towards the center where it passes out.

As the cleaner blades reach their inner posi tion limit switch 29 will be moved to the right by finger 21 (Figure 3) to open the circuit of holding coil 9 of switch I3. During the above described operation of the slow speed and cleaner motors the high speed motor which is permanent- 1y geared to the basket will be driven by the low speed motor at such speed that governor I2 opens the circuit of coil I5. Consequently when coil 9 is deenergized by limit switch 29, switch I3 drops open and switch 45 closes. The closing of switch I energizes the high speed motor which begins to accelerate to the normal high speed necessary for the proper operation of the centrifugal extractor basket. Since switch I3 controls the circuits of motors 2', I2, and 4 these motors can receive no current after this switch is opened by switch 29 and these motors stop. Low speed motor 2 is not driven by high speed motor 3 due to the interposition of the free wheeling or overrunning clutch between motor 2 and the gear casing I.

The high speed motor now accelerates until the basket has attained its normal operating speed.

The timer 55 will be adjusted to energize coil 55 which operates switch 49 to start valve motor 6 The ficient quantity of sludge has passed to the machine timer 58 energizes coil 51 which through switch 52 closes a. reverse circuit for motor 6 and the valve is closed and switch 52 opens leaving the valve in closed position.

At the time valve is closed, or at a definite time after to give a drying period for driving allthe water from the basket, the timer 59 operates to throw the reversing switch 42 which plugs motor 3 and quickly slows it down to a speed where governor I2 closes the circuit of coil I5 which opens switch 45 of the high speed motor, and timer 59 opens the circuit of coil Bil whereupon switch 42 returns to position for normal forward running of motor 3.

The closing of switch I3 energizes the slow speed motor, the cleaner motor and the jogging timer motor. The starting of the cleaner motor releases limit switch 29 which closes the holding coil 9 of switch I3 and as the slow speed motor attains normal speed governor I2 opens the cir cult of coil and the cycle of operation is completed and will termittent due to the operation of the jogging timer. The jogging time may be varied by varying the faces of the cam on the jogging timer. The slow speed motor operates until the cleaner blades return to their starting position and stop. The main motor will then start and accelerate to bring the extractor basket up to normal operating speed, at which time the inlet valve opens and remains open for a definite time then closes. A timer controls the length of time the main motor operates. Timers also control the time of opening and closing of the main valve and the timers are adjusted so that the valve closes before the main motor shuts down. The main motor is quickly decelerated and when it attains a. definite low speed the slow speed motor. starts up and takes control and the cycle of operation is automatically repeated. The free wheeling clutch between the slow speed motor and the gear drive permits the high speed motor to take up the load and lets the low speed motor stop.

It will also be apparent that when'the machine is started after it has been stopped for any reason it will always start with the cleaning operation. The equipment is so arranged that ii it is stopped before the end of the cycle, the individual control devices will reset and shut the equipment down, that is the sludge valve will close, the timers will reset and the motbr will.

come to rest.

The electric control of the present invention affords the facility for varying the length of time of purging, the length of tme of cleaning. the amount of inflow and the length of the post-drying period. Each one of these functions or oper ations may be controlled independently of the others and the control of the time and sequence of each provides means for a variabie cycle of operations. W

Having thus fully described my said invention,

what I claim as new and desire to secure by Letters Patent is:

1. In a. centrifugal extractor for sewage sludge and other material, in combination, a centrifugal basket, a low speed electric motor for driving said basket at low speed, a high speed electric motor for driving said basket at normal extracting speed, an, over-running clutch between the low speed motor and the basket, a source of current supply for said motors, and interlocked switches in the circuits of said motors and controlling their operation.

2. In a centrifugal extractor for sewage sludge and other material, in combination, a centrifugal basket, low and high speed electric motors for driving said basket, an over-running clutch between the low speed motor andthe basket, a source of current supply for said motors, operating circuits connecting said source with said motors, interlocked switches in said circuits, and means controlled by the speed of the high speed motor for controlling the operation of said switches.

3. In a centrifugal} extractor for sewage sludge and other material, in combination, a centrifugal basket, low and high speed electric motors for driving said basket, an over-running clutch between the low speed motor and the basket, a source of current supply forsaid motors, operating circuits connecting said source with said motors, an operating switch in the circuit of the low speed motor, an operating switch in the circuit of the high speed motor, interlocking means between said switches controlled by the speed of the high speed motor for closing the low speed motor switch and opening the high speed motor switch, and means responsive to the closure of the low speed motor switch for holding said switch in closed position.

4. In a centrifugal extractor for sewage sludge and other material, in combination, a centrifugal basket, a low speed motor, an overrunning clutch between said motor and said basket, a high speed motor geared to said basket, cleaner mechanism within said basket, a cleaner motor for operating said mechanism, a source of current supply for said motors, a switch for connecting said low speed and cleaner motors to said source in parallel, a switch for connecting said high speed motor to said source, and means interlocking said switches so that one is open when the other is closed.

5. In a centrifugal extractor for sludge and other material, in combination, a centrifugal basket, a low speed motor, an overrunning clutch between said motor and said basket, a high speed motor geared to said basket, cleaner mechanism within said basket, a cleaner motor for operating said mechanism, a source of current supply for said motors. a switch for connecting said low speed and cleaner motors to said source in parallel, a switch for connecting said high speed motor to said source, means responsive to the speed of the high speed motor for closing the low speed motor switch and opening the high speed motor switch, and means responsive to the operation of the cleaner motor for holding the low speed motor switch in closed position.

6. In a control system for a centrifugal extractor, a centrifugal extractor basket, cleaner mechanism within said basket, a cleaner motor for driving said mechanism alternately in reverse directions, a reversing switch for said motor, limit switches operated by said mechanism for controlling said reversing switch, a low sewage speed motor for driving said basket, said motors connected in parallel, a source of current supply for said motors, and. a switch controlling the circuit of both of said-.motors.

7. In a control system for a centrifugal extractor, a centrifugal extractor basket, a cleaner mechanism within said basket, a cleaner motor for driving said mechanism alternately in reverse directions, a reversing switch for said motor, and means controlled by said mechanism for operating said reversing switch, an intermittently operated switch in said cleaner motor circuit, a motor for driving said intermittent switch, a motor for driving said basket, a source of current for said motors and means connecting said motors, to said source in parallel.

8. In a centrifugal machine for sewage sludge and other material, in combination, a centrifugal basket, an electric motor for driving said basket, an inlet'valve for supplying sludge to said basket, an electric motor for opening and closing said valve, 2. source of current supply for said motors, a switch for connecting said driving motor to said source, said valve motor connected in parallel with said driving motor on the motor side of said switch, and time controlled means for controlling the valve motor.

9. In'a centrifugal extractor for sewage sludge and other material, in combination, a centrifugal basket, an electric motor for driving said basket, an inlet valve for supplying sludge to said basket, an electric motor for opening and closing said valve, a source of current supply for said motors, an operating switch in said driving motor circuit, said valve motor connected in parallel with said driving motor on the motor side of said operating switch, a decelerating device in said driving motor circuit on the line side of said operating switch, and time controlled means for controlling the valve motor and the decelerating device.

10. In a centrifugal extractor for sewage sludge and other material, in combination, a centrifugal basket, low speed and high speed driving motors therefor, cleaner mechanism within the basket, a motor for driving said mechanism, an inlet valve for supplying sludge to said basket, a motor for opening and closing said valve, 2. source of current supply for said motors, and a switch having two operating positions in one of which it connects the cleaner and slow speed motors to the source and in the other connects the high speed and valve motors to the source.

11. In a centrifugal extractor for sewage sludge and other material, in combination, a. centrifugal basket, low speed and high speed driving motors therefor, cleaner mechanism within the basket, a motor for driving said mechanism, an inlet valve for supplying sludge to said basket, a motor for opening and closing said valve, a source of current supply for said motors, means for connecting the cleaner motor and low speed motor to the source, and means responsive to an operation of the cleaner motor for disconnecting these motors and connecting the high speed motor to the source.

12. In a centrifugal extractor for sewage sludge and other material, in combination, a centrifugal basket, low speed and high speed driving motors therefor, cleaner mechanism within the basket, a motor for driving said mechanism, an inlet valve for supplying sludge to said basket, a motor for opening and closing said valve, a, source of current supply for said motors, time controlled means for energizing the aososn valve motor to open and close the inlet valve, and time controlled means for slowing down the high speed motor.

13. In a centrifugal extractor for sewage sludge and other material; in combination, a centrifugal basket, low speed and high speed driving motors therefor, cleaner mechanism within the basket, a motor for driving said mechanism, an inlet valve for supplying sludge to said basket, a motor for opening and closing said valve, a source of current supply for said motors, means for connecting the cleaner motor and low speed motor to the source, means re- I said cleaner motonmeans for periodically energizing and deenergizing said cleaner motor, a Jogging motor foroperatlng said periodicmeans, an inlet valve for supplying sludge to said basket, a time controlled motor for opening and closing said valve, time controlled means for slowing "down the high speed driving motor, means responsive to a low speed of the high speed motor to deenergize the high speed motor and energize' the low speed, cleaner and jogging motors, and means responsive to an operation of the cleaner mechanism for deenergizing the low speed, cleaner and jogging motors and energizing the highspeed motor. v

15. In a centrifugal extractor for sewage sludge in combination, a centrifugal basket, a motor for driving said basket at low speed, cleaner mechanism within said basket, a cleaner motor for driving said mechanism, a source of current supply for said motors, and-means controlled by said cleaner mechanism for reversing the cleaner motor, said means also controlling the stopping of both the low speed driving and cleaner motors.

16. In a centrifugal extractor, in combination, a centrifugal basket, a motor for driving said basket, cleaning blades located within said basket and movable back and forth from the center towards the inner wall of said basket, a cleaner motor for oscillating said blades, a reversing switch for said cleaner motor, limit switches onerated by said cleaner motor in the extreme positions of said blades for operating said reversing switch, a source of current for said motors, for means connecting said motors to said source in parallel, and means controlled by one of said limit switches for controlling said means;

17. In a centrifugal extractor, in combination, a centrifugal basket, a motor for driving said basket, cleaning blades mounted within said basket to oscillate from the center towards the inner wall of said basket, a source of current supply for said motors, a switch for connecting said motors in parallel to said source, a holding coil for said switch, and means operated by said cleaner motor for deenergizing said holding coil when the cleaning blades are in their extreme center position.

18. In a centrifugal extractor, in combination,

a centrifugal basket, a motor for driving said basket, cleaning blades mounted within said basket to oscillate from the center towards the inner wall of said basket, a source of current supply for said motors, a switch for connecting said motors in parallel to said source, a holding coil for said switch, means operated by said cleaner motor for deenergizing said holding coil when the cleaning blades are in their extreme center position, and a reversing switch for the. cleaner motor controlled by said means.

19. In a centrifugal extractor, in combination, a centrifugal basket, a motor for driving said basket, cleaning blades mounted for oscillatory movement in the basket, a reversible cleaner motor for oscillating said blades, a reversing switch'for said cleaner motor, a periodic switch controlling said cleaner motor circuit to give a step-by-step movement of the blades in both directions, a motor for operating said periodic switch, a source of current supply for said motors,

a switch for connecting said motorsin parallel to said source, a holding soil for holding said connecting switch in closed position, and means operated by the cleaner motor when the blades are in extreme inner position for. deenergizing said holding coil. 7 1

20. In a centrifugal extractor in combination, a centrifugal basket, low speed and high speed driving means for said basket, means for clean lngsaid basket, means responsive to an operation of the cleaning means for shifting the drive from the low speedto the high speed driving means, and time controlled means for shifting the drive from the high speed to the low speed driving means.

,2 l. In a centrifugal extractor, in combination, a centrifugal basket, a motor for driving said basket, cleaning blades mounted for outward and inward movement in the basket, a reversible cleaner motor for oscillating said blades, and means including a periodic switch for periodically operating the said cleaner motor to give the cleaning blades a step by step outward movement.

22. In a centrifugal extractor, in combination, a centrifugal basket having a bottom discharge opening, a motor for driving-said basket, clean- -ing blades mounted for outward and inward movement in the basket and having portions traversing the bottom of the basket, a reversible cleaner motor for oscillating said blades, and means including a periodic switch for periodically operating the said cleaner motor to give the cleaning blades a step by step inward movement to deflect the material on inward movement of the cleaner blades to said discharge opening.

23. In a centrifugal extractor, in combination, a centrifugal basket, a motor for driving said basket, cleaning blades mounted for outward and inward movement in the basket, a reversible cleaner mo or for oscillating said blades, and means including. a periodic switch for periodically operatlng'the said cleaner motor to give the clean. lng blades a step by step outward and lows movement. I

24. In a control system for a centrifugal ext-ac tor, a basket, cleaner mechanism for said basket. an electric motor for driving said mechanism alternately in reverse directions, a reversing switch for said motor, and means controlled by} said mechanism for operating said reversing switch, an electric motor for driving said basket, and means for connecting said motors in parallel to a source of current supply.

25. In a centrifugal extractor for sludge oroth- CERTIFICATE OF CORRECTION.

Patent No. 2,080,874. May 18, 1937,

JOSEPH S. PECKER.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, first column, line 56, for "10" read 45; and page 5, first column, line 60-61, for "for means" read means for; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 29th day of June, A. D. 1937.

Henry Van Arsdale (Seal) v Acting Commissioner of Patents. 

